The present disclosure relates to systems and methods of plugging a wellbore for abandonment and, more particularly, using a casing cutting tool having fluid jet nozzles for removing wellbore casing in preparation for the placement of a cement plug.
In the oil and gas industry, once a hydrocarbon bearing well reaches the end of its useful life, the well is decommissioned for abandonment. Regulations under various state and federal laws require decommissioned wells to be properly plugged and sealed using various “plug and abandonment” procedures before abandoning the well. Plug and abandonment operations performed in a cased wellbore require that certain portions of the wellbore be filled with cement to prevent the upward movement of fluids towards the surface of the well. To seal the wellbore, a bridge plug is typically placed at a predetermined depth within the wellbore and cement is then introduced to form a column of cement high enough to ensure that the wellbore is permanently plugged.
In addition to simply sealing the interior of the wellbore, state and federal regulations also often require that an area outside of the wellbore be sufficiently blocked to prevent any fluids from migrating towards the surface of the well along the outside of the casing string. For example, in well completions having multiple strings of casing lining the wellbore, the annular area between the concentric strings can form a fluid path in spite of being cemented into place when the well was initially completed. The combination of bad cement jobs and weakening conditions of cement over time can lead to paths being opened in the cement that may facilitate the passage of fluid to the surface.
In order to ensure the area outside of the wellbore is adequately blocked, cement is typically injected or “squeezed” through perforations in the casing and into the formation surrounding the wellbore. By pumping cement in a non-circulating system, a predetermined amount of cement may be forced into the surrounding formation and can thereafter cure to form a fluid barrier. In cases where the wellbore to be plugged and abandoned has an outer string of casing and an inner string of casing coaxially disposed therein, the annular space between the concentric strings must be squeezed with cement to prevent the subsequent migration of fluid towards the surface of the well.
The cement squeeze approach, however, does not guarantee that the cement fully contacts the surrounding formation since the cement is typically required to pass through a narrow passage which may or may not allow the cement to reach all areas at the rock phase. As a result, the plug job may be compromised and rendered at least partially ineffective. Another approach that exposes the surrounding rock formation is reaming out the wellbore over the desired area. Reaming, however, is quite time consuming and costly and therefore not a viable alternative in some wells.